Number of Participants Experiencing the Occurrence of at Least One Treatment-emergent Adverse Event (TEAE) During the Evaluation Period From Entry Visit 1 Through End of Treatment (Approximately 6.5 Years). [ Time Frame: From entry Visit 1 through end of treatment (approximately 6.5 years) ] [ Designated as safety issue: No ]

Adverse events are any untoward medical occurrences in a subject administered study treatment, whether or not these events are related to treatment.

Number of Participants Experiencing the Occurrence of at Least One Serious Adverse Event (SAE) During the Evaluation Period From Entry Visit 1 Through End of Treatment (Approximately 6.5 Years). [ Time Frame: From entry Visit 1 through end of treatment (approximately 6.5 years) ] [ Designated as safety issue: No ]

A Serious Adverse Event (SAE) is any untoward medical occurrence that at any dose:

Is fatal

Is life-threatening

Results in persistent or significant disability/incapacity

Requires inpatient hospitalization

Prolongs existing inpatient hospitalization

Is a congenital anomaly/birth defect

Is considered to be an important medical event. Such an event may not be immediately life threatening or result in death or hospitalization but may jeopardize the subject or may require intervention to prevent one of the other outcomes listed in the definitions above

Original Primary Outcome Measures ICMJE (submitted: October 17, 2007)

To assess the tolerability and safety of long-term lacosamide administration in subjects with painful distal diabetic neuropathy. Assessment of adverse events, changes in laboratory parameters, ECGs, and physical examinations. [ Time Frame: Assessments are made at all clinic visits. ]

The PGIC is a 7-point self-administered categorical rating scale in which the subject rated the change in pain since starting trial medication (from much worse [score of 1] to much better [score of 7]).

Reported results are presented as Better (sum of mildly, moderately, or much better), No Change, or Worse (sum of mildly, moderately, or much worse).

The secondary objective is to evaluate the efficacy of long-term use of lacosamide in this indication. Efficacy will be determined by pain score ratings assessed in a patient's diary and with ratings at the clinic visits. [ Time Frame: Efficacy will be determined by pain score ratings assessed in a patient's diary for daily entries and with ratings at the clinic visits. ]

A Multi-center, Open-label, follow-on Trial to Assess the Long-term Safety and Efficacy of Lacosamide in Subjects With Painful Distal Diabetic Neuropathy Including a Double-blind, Randomized Time Point Withdrawal Subtrial.

Brief Summary

SP746 (NCT00546351) is a multi-center, open-label, follow-on trial. The purpose of this trial is to assess safety and tolerability of long-term exposure of lacosamide (previously referred to as SPM 927) in subjects with painful distal diabetic neuropathy.

SP743 (NCT00238524) or SP874 (NCT00350103) due to lack of efficacy or due to intolerability to trial medication (after Visit 5but prior to entering the Maintenance Phase) may be eligible to participate in SP746 (NCT00546351), after consultation with the medical monitor